1. Field of the Invention
The present invention relates to a separator interposed between adjacent ones of rolling elements (e.g., rollers) of a linear guide apparatus, as well as a linear guide apparatus.
2. Description of the Background Art
In a linear guide apparatus, a slider relatively moves with respect to a guide rail while pluralities of rolling elements roll in endless circulation passages. If the slider relatively moves with respect to the guide rail, the rolling elements roll in the same direction, so that adjacent ones of the rolling elements rub against each other. For this reason, there are problems in that a smooth rolling of the rolling elements is hampered, a wear of the rolling elements progresses fast, and noise increases. Accordingly, in order to operate the linear guide apparatus by allowing the rolling elements smoothly, by preventing early wear of the rolling elements, and by suppressing the generation of noise, a linear guide apparatus is known in which a separator (retaining piece) is interposed between adjacent ones of the rolling elements (e.g., rollers).
For example, in a technique disclosed in Japanese Patent Unexamined Publication No. JP-A-10-110728, a linear guide apparatus is proposed in which the separators are connected together by a flexible belt-shaped connector (hereafter referred to as the “belt-shaped arm portion”).
However, with the separators connected together by the belt-shaped arm portion, the belt-shaped arm portion is repeatedly bent when the belt-shaped arm portion transfers from a linear motion area to a direction changing passage area of the endless circulation passage. At this time, a relatively large force acts in the thus bended portion of the belt-shaped arm portion in the direction changing passage area. For this reason, if this bending is repeated, there is a risk of the belt-shaped arm portion fracturing due to the fatigue of the material. Further, there is a possibility that an operational malfunction such as a locking of the circulating rollers can occur depending on thus fractured position of the belt-shaped arm portion. In addition, in a case where the fracture of the belt-shaped arm portion has occurred, after all the rollers in the endless circulation passage are temporarily pulled out, and the belt-shaped arm portion where the fracture occurred is removed, and then, a need arises to build in all the rollers again. For this reason, it cannot necessarily be said that the construction of the separators as a unit is good when taking into account of performing maintenance.
Accordingly, it has been conceived to interpose an independent separator 150 between adjacent ones of rollers 46, as shown in FIG. 12. This separator 150 has a pair of arm portions 152 for retaining the adjacent rollers 46 in a predetermined attitude. The separators 150 are incorporated in an endless circulation passage 28 alternately with the rollers 46, such that each of their arm portions 152 is retained (guided) in a guide groove 38 formed by a retainer 40 and the like. Hence, the separators 150 are capable of lessening the axial waggling (skew) and competitive rolling of the rollers 46, thereby making it possible to stably circulate the rollers 46.
If such a construction is adopted, a large cumulative force is practically not applied to the arm portions 152 of the separators 150 during the circulation in the endless circulation passage 28. For this reason, the possibility of occurrence of the operational malfunction such as the locking of the circulating rollers becomes small.
The separators 150 having the above-described construction are incorporated in the endless circulation passage 28 independently as individual parts. At this time, there are cases where the rollers 46 and the separators 150 are inserted into the endless circulation passage 28 from outside the retainer 40. In this case, as shown in FIG. 13, the separator 150 (the separator shown in the center of the drawing) is set horizontally and is inserted in the direction in which the retainer 40 continues. Subsequently, the separator 150 is rotated and is set in a perpendicular direction (predetermined position). It should be noted that in FIG. 13, an image in which the separator 150 is set horizontally and is inserted, and the separator 150 is subsequently rotated and is set in the perpendicular direction (predetermined position) is shown by solid arrows.
Thus, if the respective separators 150 are incorporated in the endless circulation passage 28 independently as individual parts, even if some operational malfunction occurs to anyone of the rollers 46 and the separators 150, for instance, they can be individually replaced. Accordingly, in performing the maintenance, for example, only the separator 150 or the roller 46 in which the malfunction has occurred can be replaced by inserting replacement parts individually into the guide grooves 38 formed by the retainer 40 and the like. As a result, as compared with the separators connected by belt-shaped arm portions, for example, it is possible to perform maintenance such as the parts replacement in less time and trouble.
Here, in the above-described separator, which has the pair of arm portions for holding the rollers in a predetermined posture and is incorporated in the endless circulation passage independently as an individual part, each of the arm portions should preferably extend to a vicinity of the center of each of the adjacent rollers, in order to prevent the axial waggling (skew) of the rollers and stabilize the posture of the rollers. In addition, the shape of the arm portion should preferably be such that the separator itself is capable of alleviating the frictional force at the time of circulation in the endless circulation passage and of improving the operability.
However, in a case where each arm portion of the separator is merely formed by being extended to the vicinity of the center of each adjacent roller, there are cases where, depending on the shape of the arm portion, particularly a distal end (free end) of the arm portion interferes with the retainer and the guide groove formed by the retainer and the like, as shown in FIG. 13. In FIG. 13, it should be noted that an image in which the arm portions of the separator interfere with the guide grooves are shown by hollow arrows.
Here, the term “interference” referred to herein means interaction occurring at a point where two or more members come into contact with each other at an identical point.
If the degree of interference of the distal end (free end) of the arm portion with the retainer and the guide groove formed by the retainer and the like is strong, there is a possibility that damage such as the bending of the arm portion can occur. For this reason, an assembly operator must perform the assembly operation while paying attention so that damage and the like do not occur in the arm portions of the separators. Accordingly, there is a problem in that the operational efficiency declines, and the assembling cost becomes high. In addition, also when the separators circulate in the endless circulation passage, if the arm portion of the separator and the wall of the guide groove interfere strongly, the sliding resistance during circulation becomes large, so that there is a problem in that smooth circulation is impaired.
In addition, in a conventional linear guide apparatus, a connecting passage is formed by a return passage provided in a slider body of a saddle-like slider and a direction changing passage provided in an end cap. A load passage is formed by causing the pair of rail raceway surfaces provided on a side surface of a guide rail and a pair of slider raceway surfaces provided on the slider body of the slider to oppose each other. Each separator is interposed between adjacent ones of the rollers, which circulate while rolling in a circulation passage formed by the connecting passage and the load passage. A pair of roller retaining holes for respectively retaining the rollers are respectively provided in front and rear sides in a circulation direction of the separator. Collar portions which come into surface contact with side surfaces of the rollers are alternately provided on side portions of the front and rear roller retaining holes, such that one side surface of one roller is brought into surface contact with the collar portion, while the axial movement of the other side surface is restricted by the wall surface of the circulation passage, to thereby prevent the contact between the rollers (e.g., Japanese Patent Unexamined Publication No. JP-A-2001-132745 (pp. 4 to 6, FIG. 5)).
Generally, the rollers, which roll along the circulation passage of the linear guide apparatus using rollers, circulate while rolling on the raceway surface in the load passage by substantially pure rolling motion.
In this case, if a skew in which the roller moves obliquely with its axis inclined obliquely without being perpendicular to the circulation direction occurs in the load passage (the angle of inclination from the perpendicular direction at this time is referred to as the skew angle), slippage occurs between the roller and the raceway surface, with the result that the movement resistance when the slider moves linearly on the guide rail increases due to the sliding frictional force. At the same time, wear is likely to occur at the rolling surfaces of the rollers and the raceway surfaces of the guide rail and the slider, which can cause a decline in life time of the linear guide apparatus.
However, with the above-described conventional technique, one side surface of the roller is brought into surface contact with each of the collars, which are provided alternately in the retaining holes of the separators, while the other side surface is restricted by the wall surface of the circulation passage to retain the rollers by the separators. Therefore, when the skew has occurred in the roller, and a corner of the other side surface of the roller has abutted against the wall surface of the circulation passage, a corner of one side surface abuts against the collar portion of the separator to move the separator in the axial direction, unfavorably causing the side surface of the other roller fitted in the same separator to be pressed against the wall surface of the circulation passage. Hence, there is a problem in that the movement resistance of the slider when the skew has occurred is increased as the frictional force between the side surface of the roller and the wall surface is added to the sliding frictional force caused by the skew.
Furthermore, with another conventional linear guide apparatus, the connecting passage is formed by the return passage provided in the slider body of the saddle-like slider and the direction changing passage provided in the end cap. The load passage is formed by causing the pair of rail raceway surfaces provided on a side surface of the guide rail and the pair of slider raceway surfaces provided on the slider body of the slider to oppose each other. The rollers are charged in the circulation passage formed by the connecting passage and the load passage, and are circulated while rolling. A pair of roller contact surfaces for respectively retaining the rollers with an adjoining portion interposed therebetween are respectively provided on front and rear sides of the separator in the circulation direction of the rollers, and a number of kinds of separators are set unequally by slightly varying the thickness of the adjoining portion. These separators are each interposed between adjacent ones of the rollers, and the rollers arranged at unequal pitches (e.g., Japanese Patent Unexamined Publication JP-A-10-281154 (mainly pp. 5 to 6, FIG. 1)).
Generally, in a case where the rollers with each separator interposed therebetween are charged in the circulation passage of the linear guide apparatus, since the separators and the rollers are separated parts, clearances are formed. If the circulation direction clearance (which refers to the clearance in the circulation direction which is formed by sequentially arranging all the rollers in the circulation passage via the separators and making them adjacent to each other) is excessively large, the separators can fall or, the posture of the separators becomes inclined, causing the separators to come into contact with the circulation passage, thereby hampering the smooth movement of the slider.
In addition, if the circulation direction clearance is excessively small, the contact pressure between the separator and the roller becomes locally high, which produces variations in the moving force during the movement of the slider.
Accordingly, a management of the circulation direction clearance to make in an appropriate range is important in achieving smooth the movement of the slider of the linear guide apparatus.
However, with the above-described conventional techniques, since a number of kinds of the separators are each interposed between the rollers in a state that the thickness of the adjoining portion is slightly varied are combined, if an attempt is made to properly set the circulation direction clearance when the circulation direction clearance is was improper or the combination was mistaken, it is difficult to visually identify the thickness of the adjoining portion of the interposed separator. Therefore, it is necessary to remove all the separators and the rollers from the circulation passage and then to charge them again, so that there is a problem in that time is required in the assembly of the linear guide apparatus.
In addition, since the visual identification of the separators is difficult, there is a problem in that in the inspection operation, it is difficult to conduct inspection as to which separators are combined, i.e., whether proper separators have been charged.